Sunday, June 18, 2017

UI5: per-view Internationalization - What about inheritance?

I started to learn UI5 in earnest in september 2016. Quite soon after that I wrote two blog posts about per-view internationalization:

(In case you're wondering: per-view internationalization is the ability to maintain i18n.properties files, which contain translations for human readable texts together with the view code wherein these texts appear, rather maintaining just one giant i18.properties file that contains the translations for any and all internationalized texts that appear throughout the application. I think the benefits of this idea are clear from a developer's point of view. If you're interested in more information about this concept, then please check out the two blog posts I wrote prior)

Per-view i18n and inheritance

The reason for me to revisit the topic is that I found that the method I use to figure out which i18n.properties files to load, doesn't work very well when you're using inheritance. In UI5, inheritance is achieved by calling the extend-method on the constructor you want to inherit from.

To understand why it doesn't work well, we should first define the scope and the desired behavior.

In my case, I'm using inheritence to build controllers for views that are a lot like other existing views, but with some additional features. Most if not all of the behavior (and texts) of the existing view should be copied, and I'm managing that copy by extending the controller of the existing view. It's just that we need some extra things in the view, and these extra things might bring their own internationalization texts along.

So, what we really need is to include not only the i18n files for the extended controller, we also need to load any i18n files that might be created for the views managed by the superclasses of the extended controller. We need to mind the order too: the extended view might choose to override some of the texts defined by a superclass, so the i18n texts that are closer in the chain of inheritance should be given precedence.

A Per-view i18n solution that works with inheritance

The following code will solve this problem:
    _initI18n: function(){
      //first, check if we already constructed the i18n model for this class
      if (this.constructor._i18Model) {
        //we did! Don't do all that work again, just use the existing one.
        this.setModel(this.constructor._i18Model, i18n);
        return;
      }

      //check if the view and controller are in the same directory.
      //if they are not, then we need to take the possibility into account 
      //that the view and the controller might both have their own i18n files.
      var stack = [];
      var controllerClass = this.getMetadata();
      var viewName = this.getView().getViewName();
      if (controllerClass.getName() !== viewName) {
        //if the view name is different from controller name, 
        //then we assume the view may have its own i18n 
        //that overrides those of the controller 
        stack.push(viewName);
      }

      //walk the chain of inheritance up to sap.ui.core.mvc.Controller
      //store each superclass at the front of the stack
      var className, rootControllerClassName = "sap.ui.core.mvc.Controller";
      while (true) {
        className = controllerClass.getName();
        if (className === rootControllerClassName) {
          break;
        }
        stack.unshift(className);
        controllerClass = controllerClass.getParent();
      }

      //walk the stack and create a resourcebundle for each class
      //use it to enhance this class' i18n model.
      stack.forEach(function(className){
        var bundleData;
        if (window[className] && window[className]._i18Model) {
          bundleData = window[className]._i18Model.getResourceBundle();
        }
        else {
          className = className.split(".");
          //snip off the local classname to get the directory name
          className.pop();  
          //add i18n to make the i18n directory name 
          className.push(i18n);
          //add i18n to point to the i18n.properties file(s) 
          className.push(i18n);
          bundleData = {bundleName: className.join(".")};
        }
        
        var i18nModel = this.getModel(i18n);
        if (i18nModel) {
          i18nModel.enhance(bundleData);
        } 
        else {
          i18nModel = new ResourceModel(bundleData);
          this.setModel(i18nModel, i18n);
        }
      }.bind(this));        

      //cache the i18n model for new instances of this class.
      this.constructor._i18Model = this.getModel(i18n);
    }
Note that this code replaces the _initI18n-method that appeared in my prior blog posts on this topic. It is also assumed that this method sits in some abstract base controller, which you'll extend to create actual concrete controllers for your views.

Here are a couple of highlights that explain the new and improved _initI18N-method:
  • Examining the entire chain of inheritance, up until sap.ui.core.mvc.Controller. This is achieved with this snippet:
          var stack = [];
          ...
          var className, rootControllerClassName = "sap.ui.core.mvc.Controller";
          while (true) {
            className = controllerClass.getName();
            if (className === rootControllerClassName) {
              break;
            }
            stack.unshift(className);
            controllerClass = controllerClass.getParent();
          }
    
    The subsequenct forEach-iteration of the stack then constructs the resource bundle to enhance the i18n model in the usual way.

    Note that names of superclasses that are "higher up" in the hierarchy (or put another way: more basal) are stacked in front of subclasses. This way, the forEach-array method will encounter the class names in the desired order, allowing the subclasess to override texts added by superclasses.
  • Distinguish between texts defined by the view and the controller.

    Admittedly this scenario is quite rare, but if the controller and view each define their own i18n files, then we'd like to enhance our i18n model with files from both resourcebundles. I somehwat arbitrarily decided that in this case, the view's texts should probably override those of the controller.

    I achieve this with this piece of code:
          var stack = [];
          var controllerClass = this.getMetadata();
          var viewName = this.getView().getViewName();
          if (controllerClass.getName() !== viewName) {
            //if the view name is different from controller name, 
            //then we assume the view may have its own i18n 
            //that overrides those of the controller 
            stack.push(viewName);
          }
    
    In other words, the view name is placed as very last item of the stack; if it differs from the controller name, then the controller name appears directly before it, making the view resource bundle the last to enhance our i18n model.
  • Caching the i18n model at the class level, so that every instance may reuse it.

    While I fixed the inheritance issue, it occurred to me that all instances of the controller would go through their own cycle of building the i18n model. Since the i18nmodel deals almost only with static texts, it seemed wasteful to repeat all that work for each instance. We can simply store the i18n model as a property of the constructor, and retrieve it any time we're creating a new instance.

    This is achieved with the very first and last bits of the _initI18n-method:
          //first, check if we already constructed the i18n model for this class
          if (this.constructor._i18Model) {
            //we did! Don't do all that work again, just use the existing one.
            this.setModel(this.constructor._i18Model, i18n);
            return;
          }
          ...
          ...
          ...
          //cache the i18n model for new instances of this class.
          this.constructor._i18Model = this.getModel(i18n);
    

Finally

I hope you enjoyed this post. Let me know and drop a line!

Saturday, June 17, 2017

Team Just-BI wins 2nd Prize at Dutch Accountability Hack 2017!

To whom it may concern,

one week ago, Friday, 9th of June 2017 I was at the Dutch house of representatives ("de tweede kamer") to participate in the 2017 Accountability Hackathon.

The Accountability Hack Event

The event was organized and sponsored by a number of Dutch ministeries, the Court of Audit ("Algemene Rekenkamer"), the Central Agency for Statistics ("Centraal Bureau voor de Statistiek") and the Open State Foundation. Goal of the event was to invite programmers, developers, data analysts, journalists and so on to come together and create applications that use one or more of the numerous open data sources published by the Dutch government to create insights in the performance or the spending of Dutch governmental or publicly subsidized organisations.

This assignment alone might need some clarification. In Dutch democracy there has always been a push towards more transparency. But in the last decade in particular, there has been an increasing demand to provide this transparency by publishing openly accessible data sets. The idea is that publishing records and metadata contributes to an environment where civilians can answer any question about how their government is functioning themselves, by querying and combining their data. Now, obviously, not everybody is capable of working with raw data sets, so there is also a demand for tools, applications and people with know-how bridge the technical gap and truly making all this data available on a functional level.

This is where events like the Accountability Hackathon come in: it is a direct attempt to stimulate individuals, but also commercial companies to apply their expertise to create applications and tools that provide meaningful information and insights, based on open data.

Team Just-BI

I participated on behalf of my company Just-Business Intelligence. Just-BI provides end-to-end Business Intelligence consultancy. I'm in the custom development branch, which creates web and mobile applications in the realm of self-service and operational Business Intelligence.

Just BI has a policy of assigning consultants to billable projects for at most 80% of their working time; The remaining 20% is meant to be invested in knowledge development. We try to align agendas and meet each other every friday at our office in Rijswijk.

This arrangement made it possible for me to attend an event like the Accountability Hackathon - in fact, Just-BI stimulates its consultants to reach out and participate in events like these.

Submission: Jubilant

The Just-BI submission is a generic OData query and exploration tool called Jubilant (short for Just Business Intelligence Analysis Tool).



Jubilant is an Open UI5 web application that provides a plugin architecture that makes it easy for developers to write their own data visualisations based on OData services. Jubilant provides rich metadata about OData services, as well as a number of reusable components that make it easy to quickly build a query editor/designer.

The Jubilant concept allows a plugin developer to focus on making a cool visualisation, without having having to invest time and effort to provide the user with a query builder. During the hackathon I managed to create two plugins - one simple table visualisation, which simply renders raw data in a data grid, and a OData Metadata Graph visualiser, which plots the structure, entity types and relationships exposed by the OData service as a graph.

OData and Open Data

The connection to open data and the assignment for the Accountability Hack is that a number of key open data API's use the OData protocol. A good example is the Dutch Parliament API.

Interestingly, there are relatively few OData query tools available, and none of them are particularly affordable. In fact, during the accountability hackathon a few teams tried to work with these OData APIs and discovered they didn't quite know how to access and process them. I don't know if this finding influenced the jury in any way, but it certainly highlighted the need for a tool like Jubilant.

For Just-BI OData is a key protocol as well, since it happens to be the standard way of exposing data by many SAP products, like SAP/HANA. While Just-BI is a general end-to-end Business Intelligence shop, many of our customer engagements have a strong focus on SAP products. This is also reflected in the Open UI5 framework, which has rather good support for OData.

Result: 2nd Prize!

I was surprised, but obviously very happy to have been awarded the 2nd prize, which is good for 1.500 EUR. It is a honour and a privilege to be in a position to work on stuff I like and maybe contribute something to the transparency of the Dutch democracy. And, frankly, I just had a great time hacking!

Since this was basically just a working day for me, I decided to donate 500 EUR of the prize money to Just-Care, which is a charity supported by Just-BI.

Where to get Jubilant?

At Just-BI, we're currently working out the exact details around a release of Jubilant. I will write an update as soon as I can disclose more, but I can already say that all the work I did for the accountability hack will become available as Open Source Software in the very near future.

In the mean while, if you're interested in Jubilant and OData-based self-service BI, don't hesitate to contact me. Or contact Just-BI.

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